A particle of mass m and charge q is fastened to one end of a string of length. The other end of the string is fixed to the point O. The whole sytem liles on as frictionless horizontal plane. Initially, the mass is at rest at A. A uniform electric field in the direction shown in then switfched on. Then

Options

A. the speed of the particle when it reaches B is `sqrt((2qEl)/(m))`
B. the speed of the particle when t reaches B is `sqrt((qEl)/(m))`
C. the tension in the string when particles reaches at B is 2qE
D. the tension in the string when the particle reaches at B is zero

Answer

B, C

Explanation

Work done by tension = 0
Work done by Electric field
`= -qE xx //(1- cos 60^(@))`
`(B)(qEl)/(2)=(1)/(2)mV^(2)rArr V = sqrt((qEl)/(m))`
`(C)T-qE = (mV^(2))/(l)rArr T = 2qE`